Total γγ opacity (black solid line and grey shaded area) produced by photon field external to the blob: BLR (red and blue dashed lines) and DT (yellow dashed line). The BLR is assumed to be composed of two concentric shells one emitting the Lyα (red) and the other the Hα line (blue). Line and thermal emitters parameters are specified in Table B.2. The green line and shaded area represent the opacity due to the synchrotron photons produced by the second blob in Table B.1 (EC model). The latter is multiplied by 10³ to be comparable with the opacity due to the external photon fields. The blob is placed well within the BLR, at r = 1.1 × 10¹⁶ cm = 0.1 × R_Lyα. Frequencies are given in the observer reference frame.